This invention relates to a resin compatible size composition for glass fibers having a relatively small diameter. The size composition is intended for glass fibers useful for making yarns to produce structural braid reinforcements.
Glass fiber yarns are useful in constructing structural braid reinforcements. Glass yarns having a small fiber diameter are preferred for use in making structural braid reinforcements since the glass yarns having a small fiber diameter are generally more resistant to damage than large diameter fibers. The small diameter glass fibers are sized with a starch-base finish in a separate operation, known as slashing, to process as warp ends. However, since starch-base finishes are not resin compatible the starch size must be removed from the glass fibers, usually thermally by a heat clean process. The glass fiber is then refinished with silane coupling agents to gain resin compatibility. These desizing and refinishing steps often reduce the tensile strength of the small diameter glass fibers.
As such, continuous glass strands having a resin compatible sizing are normally available only on large filament diameter strands. However, it is not as desirable to use large diameter glass fibers since these large diameter glass strands do not process well in braiding due to the large filament diameter and the high coefficient of friction generated during the braiding process.
Considerable expense could be saved if a size composition were available for use on small diameter glass fibers which is compatible with epoxy and polyester resins and which provides a glass fiber yarn comprised of small diameter glass fibers useful for making structural braid reinforcements.
This invention is directed to the solution of that problem.